Ambient air
Ambient air is the air that surrounds a process apparatus or a plant. It consists mainly of nitrogen, oxygen, argon, water vapor, and trace gases. Ambient air enters processes when plants are not gas-tight or inerted.
In process engineering, ambient air influences oxidation, moisture uptake, and contamination. Oxygen can trigger reactions or aging processes. Water vapor can moisten hygroscopic powders and change their flow properties.
Air humidity is often described by relative humidity:
Φ = pH2O / psat(T)
- ϕ the relative humidity
- pH2O is the water vapor pressure
- psat(T)is the saturation vapor pressure at temperature T
- T is the temperature
In explosion-hazardous areas, ambient air is relevant because it supplies oxygen for dust or gas explosions. Therefore, many processes are inerted to reduce the oxygen content.
It can be sensible to locate process engineering processes in suitable climate zones. Spray towers for drying suspensions are more economical to operate when the ambient air is clean and dry. Low air humidity reduces the energy demand for drying and increases process stability.
Ambient air is deliberately used or deliberately excluded in drying, cooling, pneumatic conveying, and filtration processes.